1. Field of the Invention
The present invention relates to a variable capacity compressor. The present invention is applicable to refrigerant compressors, in particular, variable capacity compressors having single-head-type pistons.
2. Description of Related Art
There has been a variable capacity compressor which is a wobble type or a swash type and which is mainly employed for vehicle air-conditioners. The variable capacity compressor has a cam plate which is connected with a rotor by way of a hinge mechanism and which is to be oscillated around a fulcrum. The compressor varies a pressure of a crankcase chamber having the cam plate, controlling a force working to the rear surface of the single-head-type piston, and balancing the rear surface and the front surface of the single-head-type piston. Accordingly, the compressor varies an inclination angle of the cam plate around the fulcrum of the cam plate. Namely, the compressor varies a piston-stroke.
The compressor sucks a refrigerant gas, which returns from an exterior refrigerating circuit, from a suction chamber, supplying the sucked refrigerant gas into bores by reciprocating the pistons, compressing the refrigerant gas, and thereby discharging the refrigerant gas into a discharge chamber. As aforedescribed, the compressor has a construction in which the refrigerant gas doesn't pass through the crankcase chamber but directly flows into the bores fitting the corresponding pistons. Accordingly, lubricating ability with respect to sliding parts disposed in the crankcase chamber depends on a blow-by gas leaked to the crankcase chamber. Also, lubricating ability with respect to the sliding parts in the crankcase chamber depends on lubricating oil contained in the refrigerant gas in discharge pressure which is positively supplied into the crankcase chamber during capacity-control to change the pressure in the crankcase chamber.
The conventional compressor is provided with a shaft sealing member arranged for sealing an exposed end portion of the drive shaft. Since the shaft sealing member is arranged in a shaft hole, located apart from the crankcase chamber, the refrigerant gas flowing toward the shaft sealing member is extremely decreased in quantity. As a result, the compressor causes secondary anxiety that the shaft sealing member is heat-deteriorated by shortage of the lubricating and the cooling, and that a clutch slips by gas-leakage.
Japanese Unexamined Patent Publication No. 7-332,250 discloses the compressor in which an appended passageway is disposed in the inside of a drive shaft along a shaft centre thereof. One end passageway portion of the appended passageway is opened in a shaft hole of a front housing, and another end passageway portion of the appended passageway is communicated with a suction pressure area. Also, this publication discloses a technique that the refrigerant gas in the crankcase chamber flows into the suction pressure area by way of the neighborhood of the shaft sealing member.
Judging from view that it is preferable that the shaft sealing member is fully lubricated and cooled, such construction concerning the publication is not satisfied. The reason is that the refrigerant gas--a flow stream from the crankcase chamber to the suction pressure area--is not limited only within the aforesaid appended passageway formed in the inside of the drive shaft. Namely, the refrigerant gas flows into the suction pressure area, not only by way of the aforesaid appended passageway but also by way of another passageway which passes through the radial bearing for supporting the drive shaft arranged in a central hole of a cylinder block.
In other words, since the refrigerant gas flows in two-passageways in the aforedescribed way, less lubricating oil is supplied to the shaft sealing member with the refrigerant gas, as a logical consequence. Also, a pressure reduction is not largely generated at a sealed portion sealed by the shaft sealing member; so, it is apparent that the conventional compressor concerning the aforesaid publication does not cool the shaft sealing member effectively.